The box H+ACA snoRNAs carry Cbf5p, the putative rRNA pseudouridine synthase
The box H+ACA snoRNAs carry Cbf5p, the putative rRNA pseudouridine synthase
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DOI：
10.1101/gad.12.4.527
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发表时间：
1998-02-15
影响因子：
10.5
通讯作者：
Tollervey, D
中科院分区：
文献类型：
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作者：
Lafontaine, DLJ;Bousquet-Antonelli, C;Tollervey, D
真核生物rRNA中的许多或所有假尿苷（Psi）形成位点通过与盒H + ACA类小核仁RNA（snoRNA）的成员进行位点特异性碱基配对来选择。先前的数据库搜索确定了大鼠核仁蛋白Nap 57 p、其酵母同系物Cbf 5 p和大肠杆菌Psi合酶truB/P35之间的高度同源性。因此，我们测试了Cbf 5 p是否是在酵母rRNA中合成Psi所必需的。在Cbf 5 p的遗传消耗后，前rRNA中Psi的形成被显著抑制，导致未修饰的rRNA的积累。蛋白A标记的Cbf 5 p共沉淀盒H + ACA snoRNA的所有测试成员，但不沉淀盒C + D snoRNA或其他RNA种类。Cbf 5 p的遗传缺失导致所有盒H + ACA snoRNA的缺失。这些包括snR 30，这是前rRNA加工所需的。Cbf 5 p的耗尽也导致与snR 30耗尽时所见类似的前rRNA加工缺陷。我们得出结论，Cbf 5 p很可能是rRNA Psi合酶，是盒H + ACA类snoRNP的一个组成部分，其功能是将酶靶向其作用位点。
Many or all of the sites of pseudouridine (Psi) formation in eukaryotic rRNA are selected by site-specific base-pairing with members of the box H + ACA class of small nucleolar RNAs (snoRNAs). Database searches previously identified strong homology between the rat nucleolar protein Nap57p, its yeast homolog Cbf5p, and the Escherichia coli Psi synthase truB/P35. We therefore tested whether Cbf5p is required for synthesis of Psi in the yeast rRNA. After genetic depletion of Cbf5p, formation of Psi in the pre-rRNA is dramatically inhibited, resulting in accumulation of the unmodified rRNA. Protein A-tagged Cbf5p coprecipitates all tested members of the box H + ACA snoRNAs but not box C + D snoRNAs or other RNA species. Genetic depletion of Cbf5p leads to depletion of all box H + ACA snoRNAs. These include snR30, which is required for pre-rRNA processing. Depletion of Cbf5p also results in a pre-rRNA processing defect similar to that seen on depletion of snR30. We conclude that Cbf5p is likely to be the rRNA Psi synthase and is an integral component of the box H + ACA class of snoRNPs, which function to target the enzyme to its site of action.